Composition. This is the makeup of the rock and includes such things as minerals and chemical elements present in the rock. The type of minerals present determines whether a rock is igneous, sedimentary, or metamorphic. For example, granite is composed primarily of quartz and feldspar while shale is composed primarily of clay and silt.
Texture. This describes how fine or coarse the grains are that make up a rock’s composition. Sandstone is coarse-textured because its grains are large compared with other rocks like granite which has a fine texture because its grains are small compared with other rocks.
Color. Some rocks have color variations due to their chemical composition; for example, iron-rich minerals produce reddish hues in some rocks such as hematite which produces red-orange tones (Figure below). Other colors come from different mineral compositions; for example, green comes from copper minerals found in stones such as malachite (Figure below) and jadeite which both produce green shades in various shades depending on how much copper they contain.
Last modified: October 8, 2022